Hi, John Stultz <john.stultz@xxxxxxxxxx> writes: > I've been tripping over an issue on my HiKey960 where with the usb-c > gadget cable connected, the gadget code doesn't consistently seem to > initialize properly. I had rarely seen this behavior previously, but > more recently it has become more frequent and annoying. > > Usually, unplugging and replugging the USB-C cable would get things > working again (but that's not helpful in test labs). > > I annotated a bunch of code trying to understand what was going on and > I narrowed down the difference in the good and bad case to a dwc3 > reset interrupts happening after usb_gadget_probe_driver() completes. > In the good case, we see the reset interrupts, and in the failed case > we don't. > > [ 16.491953] JDB: usb_gadget_probe_driver > [ 16.495938] JDB: udc_bind_to_driver > [ 16.499555] JDB: dwc3_gadget_start irq: 65 revision: 1429417994 > [ 16.503803] JDB: __dwc3_gadget_ep_enable > [ 16.507791] JDB: __dwc3_gadget_ep_enable > [ 16.511715] JDB: dwc3_gadget_enable_irq > [ 16.515582] JDB: usb_udc_connect_control > [ 16.519510] JDB: usb_gadget_connect > <in the bad case, this is all we see, the gadget device doesn't come up> > [ 16.811010] JDB: dwc3_gadget_interrupt > [ 16.814783] JDB: dwc3_gadget_reset_interrupt > [ 16.819047] JDB: dwc3_reset_gadget > [ 16.823935] JDB: dwc3_gadget_interrupt > [ 16.827686] JDB: __dwc3_gadget_ep_enable > [ 16.831611] JDB: __dwc3_gadget_ep_enable > [ 16.994477] JDB: dwc3_gadget_interrupt > [ 16.998246] JDB: dwc3_gadget_reset_interrupt > [ 17.002519] JDB: dwc3_reset_gadget > [ 17.005922] JDB: usb_gadget_udc_reset > [ 17.062422] JDB: usb_gadget_set_state state: 5 > [ 17.067069] JDB: dwc3_gadget_interrupt > [ 17.070823] JDB: __dwc3_gadget_ep_enable > [ 17.074745] JDB: __dwc3_gadget_ep_enable > [ 17.170898] JDB: usb_gadget_set_state state: 6 > [ 17.195605] JDB: usb_gadget_set_state state: 7 > [ 17.200179] JDB: __dwc3_gadget_ep_enable > [ 17.204118] JDB: __dwc3_gadget_ep_enable > [ 17.208057] JDB: usb_gadget_vbus_draw > [ 17.211721] JDB: usb_gadget_set_state state: 7 > <in the good case everything is happy here> > > > This sounds a bit like the issue in the comment here: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/dwc3/gadget.c?h=v5.8-rc3#n3143 > > However, I've tried calling dwc3_gadget_reset_interrupt() and > dwc3_reset_gadget() at the tail end of dwc3_gadget_start() but that > doesn't seem to help. > > I was curious if you or anyone else had any thoughts on how to debug > this further? Try enabling dwc3 tracepoints and collecting working and failing cases. If I were to guess, I would say there's a small race condition between setting pullup and the transceiver sending the VBUS_VALID signal to dwc3. -- balbi
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